A road roller, roller-compactor, asphalt compactor, pneumatic compactor or simply a “roller” are a compactor type vehicles used to compact soil, gravel, concrete, or asphalt in the construction of roads and foundations. Two types of compactors will be discussed here: pneumatic tire compactors and drum vibratory compactors, also known as asphalt compactors because of their predominant use on asphalt. Both types of compactors do the same type of work in different ways.
Drum vibratory compactors offer contractors a high productivity solution for finishing asphalt. In the vibratory mode, drum compactors quickly increase the density of fresh asphalt and are usually the preferred machine for the initial breakdown pass in most applications. After the breakdown pass, either a drum or a pneumatic-tire compactor is used to continue compaction. Tandem steel-drum machines, with their ability to vibrate the surface, may achieve the required level of density in roughly half the number of passes as a pneumatic-tire machine in the intermediate rolling applications.
One key difference is that steel drums leave behind a surface that is more permeable and open textured. Many state departments of transportation are using permeable asphalt pavements designed to let rain migrate through the top asphalt layer to drainage channels underneath. In areas with high rainfall amounts, the open texture is often specified because this type of road surface is better at reducing standing water and spray from passing vehicles. Open-texture asphalt pavements also give vehicles better traction and skid resistance.
One the other hand, pneumatic-tire compactors are only half as productive as tandem-drum vibratory compactors in the intermediate applications as a general rule. However, pneumatic tire compactors still play an important role in asphalt compaction. First, pneumatic-tire compactors create a smooth, impermeable wear layer. While the textured wear layers that steel drums create are gaining favor in some states, only about 15% of roadways are designed with this textured wear layers in the specifications. Smooth, impermeable wear layers drain water to the sides and prevent the water from weakening the sub-base.
Pneumatic-tire compactors are much preferred when compacting naturally occurring soils, crushed stone and chip-seal surfaces because steel drums tend to fracture these types of stone. Also, the working speed of pneumatic compactors, many of which can run from 4 to 8 mph is higher than that of a drum compactor.
Because paving trains of road construction crews are moving at faster speeds, the compaction equipment, both drum (asphalt) and pneumatic-tire compactors must, by design, keep up with paving trains for efficiency. There have been significant improvements in compaction equipment during the past decade, especially with vibratory drums, which usually rely upon an eccentric weight system within the drums. Pneumatic-tire compactors have also evolved to include hydrostatic drive systems and improved tires.
However, improvements in compaction of soils and paving materials are always desirable in terms of both the quality of compaction and the speed of compaction.